1. Field of the Invention
The invention in general relates to side looking sonar equipment and particularly to a transmitting transducer therefore.
2. Background Information
In side looking systems, the sonar apparatus is mounted on a carrier vehicle which travels along a course line at a certain altitude above the target area to be examined. A transmitting transducer propagates acoustic energy to ether side of the course line and impinges upon the target area in a relatively narrow strip, such impingement process being termed insonification. A receiver transducer receives the acoustic energy reflected from the insonfied strip and during the course of travel of the carrier vehicle, the return signals are portrayed on a line-by-line basis that is a pattern of highlights and shadows analogous to an optically viewed panorama illuminated by side lighting, with objects outlined in such a way as to permit their identification.
The carrier speed and therefore the search or mapping rate may be significantly increased by increasing the area detected and portrayed for each acoustic transmission. This is accomplished with the use of signal processing apparatus which forms a plurality of receiver beams each of which looks at a relatively narrow strip of the insonified region.
In one operating system, eight receiver beams are formed on either side of the carrier vehicle and relatively good resolution is obtained for target identification. The insonified region for the eight beam system is approximately the width of the eight beams at some minimum range of interest and slightly increases in width out to some maximum range of interest so as to define a trapezoidal pattern. This width difference is desired in order to accommodate for small variations in carrier speed as well as any oscillatory motion of the carrier vehicle about a vertical axis (yawing).
For extremely high resolution work, a system is utilized which travels at slower speeds and forms fewer and much more narrow receiver beams. A typical high resolution system may form three receiver beams and in such instance the transmitting transducer utilized in the eight beam system cannot be used for the three beam system because the insonification pattern would be too wide. Smaller transmitter transducers often used for the high resolution system cannot accommodate the power input required for the desired insonification and often experience cracking and total failure.
The side looking sonar apparatus of the present invention may be used for high resolution work and includes a transmitter transducer which can accommodate a high power input signal to properly insonify the target area.